Contraintes universelles sur la forme des lettres // Universal constraints on letter shapes

The study of the visual shape of letters in writing systems (alphabets, syllabaries, etc.) sits at the intersection of linguistics, visual cognition, and cultural evolution. A fluent reader processes thousands of letters per minute—these letters need to be instantly recognisable, distinctive, and easy to categorize. Writing systems evolved under a pressure to maximise visual features that satisfy these needs, and this left a mark on letter shapes, which, it has been argued satisfy universal or near-universal visual constraints; this hypothesis has allowed researchers to predict and discover specific visual features of letter shapes, concerning topology, orientation, or complexity (Changizi et al. 2006, Morin 2018, Kelly et al. 2021).
One thing that hinders currrent work in the area is the lack of a shared descriptive vocabulary to classify visual shapes, equivalent to what phonologists have in the international phonetic alphabet. This PhD project will build on the dataset collected with the Glyph applet, a crowdsourcing initiative were thousands of lay participants freely proposed letter shape classifications, resulting in parcimonious and complete descriptions of letter shapes in 43 scripts spanning a wide variety of languages, semiotic types, and cultural areas (Kim et al. 2025). The Glyph system remains imperfect: in particular, it lacks generality, as it requires every script to be described with its own set of visual features. A major axis of the PhD will be to achieve a fully general list of visual features, capable of describing letter shapes in any script, using a novel version of the Glyph platform that is being prepared. For this, the Glyph system can be combined with other proposals that have been put forward for standardised descriptions of line drawings (Melnik et al. 2021).
The goal of the PhD is to use a fully general description of the visual features that define letter shapes to map cross-cultural visual universals, and to find out whether letters are more discriminable than shapes lacking these precise visual universals. The work would entail a mix of experimental and data-driven approaches, and would fit a student with a Master's degree (or equivalent) in cognitive science, linguistics, linguistic or cognitive anthropology, or cultural evolution.
References
Changizi, Mark, Qiong Zhang, Hao Ye, and Shinsuke Shimojo. 2006. ‘The Structures of Letters and Symbols throughout Human History Are Selected to Match Those Found in Objects in Natural Scenes'. The American Naturalist 167 (5): E117-139. https://doi.org/10.1086/502806.
Kelly, Piers, James Winters, Helena Miton, and Olivier Morin. 2021. ‘The Predictable Evolution of Letter Shapes: An Emergent Script of West Africa Recapitulates Historical Change in Writing Systems'. Current Anthropology 62 (6): 669–91. https://doi.org/10.1086/717779.
Kim, Yoolim, Marc Allassonnière-Tang, Helena Miton, and Olivier Morin. 2025. ‘The Phonology of Letter Shapes: Feature Economy and Informativeness in 43 Writing Systems'. Journal of Memory and Language 142: 104620. https://doi.org/10.1016/j.jml.2025.104620.
Melnik, Natalia, Daniel R. Coates, and Bilge Sayim. 2021. ‘Geometrically Restricted Image Descriptors: A Method to Capture the Appearance of Shape'. Journal of Vision 21 (3): 14. https://doi.org/10.1167/jov.21.3.14.
Morin, Olivier. 2018. ‘Spontaneous Emergence of Legibility in Writing Systems: The Case of Orientation Anisotropy'. Cognitive Science 42 (3): 664–77. https://doi.org/10.1111/cogs.12550.
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The study of the visual shape of letters in writing systems (alphabets, syllabaries, etc.) sits at the intersection of linguistics, visual cognition, and cultural evolution. A fluent reader processes thousands of letters per minute—these letters need to be instantly recognisable, distinctive, and easy to categorize. Writing systems evolved under a pressure to maximise visual features that satisfy these needs, and this left a mark on letter shapes, which, it has been argued satisfy universal or near-universal visual constraints; this hypothesis has allowed researchers to predict and discover specific visual features of letter shapes, concerning topology, orientation, or complexity (Changizi et al. 2006, Morin 2018, Kelly et al. 2021).
One thing that hinders currrent work in the area is the lack of a shared descriptive vocabulary to classify visual shapes, equivalent to what phonologists have in the international phonetic alphabet. This PhD project will build on the dataset collected with the Glyph applet, a crowdsourcing initiative were thousands of lay participants freely proposed letter shape classifications, resulting in parcimonious and complete descriptions of letter shapes in 43 scripts spanning a wide variety of languages, semiotic types, and cultural areas (Kim et al. 2025). The Glyph system remains imperfect: in particular, it lacks generality, as it requires every script to be described with its own set of visual features. A major axis of the PhD will be to achieve a fully general list of visual features, capable of describing letter shapes in any script, using a novel version of the Glyph platform that is being prepared. For this, the Glyph system can be combined with other proposals that have been put forward for standardised descriptions of line drawings (Melnik et al. 2021).
The goal of the PhD is to use a fully general description of the visual features that define letter shapes to map cross-cultural visual universals, and to find out whether letters are more discriminable than shapes lacking these precise visual universals. The work would entail a mix of experimental and data-driven approaches, and would fit a student with a Master's degree (or equivalent) in cognitive science, linguistics, linguistic or cognitive anthropology, or cultural evolution.
References
Changizi, Mark, Qiong Zhang, Hao Ye, and Shinsuke Shimojo. 2006. ‘The Structures of Letters and Symbols throughout Human History Are Selected to Match Those Found in Objects in Natural Scenes'. The American Naturalist 167 (5): E117-139. https://doi.org/10.1086/502806.
Kelly, Piers, James Winters, Helena Miton, and Olivier Morin. 2021. ‘The Predictable Evolution of Letter Shapes: An Emergent Script of West Africa Recapitulates Historical Change in Writing Systems'. Current Anthropology 62 (6): 669–91. https://doi.org/10.1086/717779.
Kim, Yoolim, Marc Allassonnière-Tang, Helena Miton, and Olivier Morin. 2025. ‘The Phonology of Letter Shapes: Feature Economy and Informativeness in 43 Writing Systems'. Journal of Memory and Language 142: 104620. https://doi.org/10.1016/j.jml.2025.104620.
Melnik, Natalia, Daniel R. Coates, and Bilge Sayim. 2021. ‘Geometrically Restricted Image Descriptors: A Method to Capture the Appearance of Shape'. Journal of Vision 21 (3): 14. https://doi.org/10.1167/jov.21.3.14.
Morin, Olivier. 2018. ‘Spontaneous Emergence of Legibility in Writing Systems: The Case of Orientation Anisotropy'. Cognitive Science 42 (3): 664–77. https://doi.org/10.1111/cogs.12550.
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Début de la thèse : 01/10/2026

Public funding alone (i.e. government, region, European, international organization research grant)

Concours pour un contrat doctoral

Ecole normale supérieure - PSL

662 Sciences Cognitives

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